Engine Mods 101 - Need some advice

[BAC]

if you ever decide to get the correct or near correct size tires instead of the tractor tires you now have on it

Tractor tyres?  I'm offended - you take that back! Oh, what the heck - sir, it was like that when I got here...    But seriously, they are nice almost brand new BF Goodrich radial T/As and I don't think I'll ever do enough mileage in my weekend cruiser to wear them out.

oh...i don't actually drink that cr_p myself, i just use it for cleaning psarts or give it to party guests that i dont like.

Whoops - well that one went straight over my head!  You're not a Queenslander are you?  Never did get their sense of humour...

[GLENN 70]

You could get a diff shop to do the whole thing , R&R and fit new gears ,not elcheapo gears but the brand Barnett said but it will cost about a grand or more easy .  If you just change the centre you just have to make sure it has the same yoke .  3.5 ratio might be ok for you ,depends on if you do mostly hwy driving or not . Mph x diff ratio x 336  divided by tyre hight = . Rpm , play around with the diff ratios to find a nice rpm at 62 mph .   The diff is quite a big job at home if you don't know how ,axles can get stuck and the centre is bloody heavy .

[GLENN 70]

He's not even an Aussie can't you tell (FOSTERS JOKES). But I am a Queenslander so if you want my advise you had better say sorry . .

[barnett468]

The diff is quite a big job at home if you don't know how ,axles can get stuck and the centre is bloody heavy .

this is why you entice a few of your burly friends to come over and help you by offering them all the cold, tasty, fosters lager they can hurl.

[BAC]

He's not even an Aussie can't you tell (FOSTERS JOKES). But I am a Queenslander so if you want my advise you had better say sorry . .

Sorry! (as long as you're not an XXXX drinker...)  

[GLENN 70]

  again

[barnett468]

.
Hey BAC...perhaps you could quell Glenn's ire by simply offering him some...[wait for it]....cold, tasty Fosters Lager.


Holy cr_p barn...I thought you liked Glenn

[BAC]

again

Sorry SIR? 

3.5 ratio might be ok for you ,depends on if you do mostly hwy driving or not . Mph x diff ratio x 336  divided by tyre hight = . Rpm , play around with the diff ratios to find a nice rpm at 62 mph .

Soooo, 62mph x 3.50 x 336 / 26.85" = 2716 RPM compared to what I have now: 62mph x 3.00 x 336 / 26.85" =  2328 RPM does that sound about right?

[GLENN 70]

Yep sounds about right without  me checking .  You just don't pick gear ratios out off you head ,work out what is best for you .    now 

[barnett468]

Tractor tyres?  I'm offended - you take that back! Oh, what the heck - sir, it was like that when I got here...    But seriously, they are nice almost brand new BF Goodrich radial T/As and I don't think I'll ever do enough mileage in my weekend cruiser to wear them out.

Well perhaps you could put an add for them in the farmers gazette and buy some actual car tires after they sell.

Whoops - well that one went straight over my head!

Why are we not surprised.

Never did get their sense of humour...

Well if you happen to drink Fosters Lager, that would explain a lot of things.


OMG barn...he's gonna kick yer a_s if he ever sees you.

[barnett468]

Soooo, 62mph x 3.50 x 336 / 26.85" = 2716 RPM compared to what I have now: 62mph x 3.00 x 336 / 26.85" =  2328 RPM does that sound about right?

jesus, here ya go. 

http://www.wallaceracing.com/gear-speed.php

[BAC]

jesus, here ya go. 

http://www.wallaceracing.com/gear-speed.php

No worries, my maths is pretty good. 

More interested if people think 2700 RPM @100 km/h is OK for the old Windsor if it does most of its cruising at 80 or less.

[GLENN 70]

2700 rpm is a bit high for a stocko ,and it will be higher at 110 Kph.  2500 would be nicer on the high way at 100 kph even tho you say you cruise at 80 most of the time .

[barnett468]

More interested if people think 2700 RPM @100 km/h is OK for the old Windsor if it does most of its cruising at 80 or less.

i wouldn't want to do it for more than an hour and certainly not on a long trip, so you need to decide what is more important to you as far as if you want a tire roaster, or freeway flier or inbetween and do that and live with the rest.

you can cheat a little by running gears that are slightly more freeway oriented then run a high stall converter for decent off the line perf to compensate for the taller gears.

i can guarantee you this...if you want to improve the cornering, the very first thing i would do is install lower profile tires . . this will also increase straight line stability a little.

[BAC]

OK, got under car and had a look at the diff and amazingly enough the tag is still on there.

Consensus from the online tag decoders is that it is a 3.00 open 28 spline unit, so if I wanted to keep to 2500 RPM at 100 km/h with my 'tractor' tyres, the shortest gear set I could use would be 3.25:1.

[barnett468]

OK, got under car and had a look at the diff and amazingly enough the tag is still on there.

Consensus from the online tag decoders is that it is a 3.00 open 28 spline unit, so if I wanted to keep to 2500 RPM at 100 km/h with my 'tractor' tyres, the shortest gear set I could use would be 3.25:1.

well just going up to 3.25 will still make a noticeable diff but not a drastic day and night diff, but if it was me, i would still put my money there...i really, really would . . yes it sounds like a lot of money for such a small change but its not a perfect world, lol . . unfortunately, you need what you need to achieve your goals, its that simple.

[GLENN 70]

If you put a 3.25 ratio in from a 3.00 and  if you really notice the difference I will be a monkey s uncle . Your tyres are a little tall at 26.9 inches and you could go to a 225/60 x15 and that will drop the gear ratio down just a little more than fitting a 3.25 diff . A lot easier and cheaper and then sell your 215/70 tyres . Just an option

[barnett468]

.

[barnett468]

.
i was bored . . here's a very close reference guide

changing from 3.00 to 3.25 with your current tires raises the rpm at 60 mph by 200.

changing your tires to 225 x 60 - 15 and leaving the 3.00 gears raises the rpm at 60 mph by 100.

changing your gears only will make exactly twice as much difference as changing your tires only will.

ive done most of the combos below and many have been the 3.25 with 235 x 60 - 15 tires or 245 x 60 – 15 tires with around a 2000 rpm stall and mild to moderate builds and they have very decent acceleration imo.

215 x 70 – 15 = 26.85 tire
3.00 = 60 mph = 2250 rpm
3.25 = 60 mph = 2450 rpm

225 x 60 – 15 = 25.6  tire
3.00 = 60 mph = 2350 rpm
3.25 = 60 mph = 2550 rpm

235 x 60 – 15 = 26.1
3.00 = 60 mph = 2350 rpm
3.25 = 60 mph = 2500 rpm

 

[GLENN 70]

Each ford gear ratio is around 200rpm different , eg going from a 3.00 to a 3.25 ratio will raise your revs about 200 rpm .  For every inch in your tyres is about 100 rpm in top gear with a 1 to 1 box .

[barnett468]

Each ford gear ratio is around 200rpm different , eg going from a 3.00 to a 3.25 ratio will raise your revs about 200 rpm .  For every inch in your tyres is about 100 rpm in top gear with a 1 to 1 box .

glenn, i was just curious about exactly what the difference would be and those numbers are generated by a calculator, they are not guesses and i did it twice . . plus i have changed a lot of diffs by just one step and could tell the difference pretty easily.

[GLENN 70]

235/60x15 tyres are the ones I would have on my Mach 1 not 215/70 x15 .  Depends one his rim width ,but should be at least a 7 inch .  Even a 235/60 can look small if the car sits high in the back .  That car should go ok now ,but we still don't know what intake it is ( dual plain or single ). And what Holley carb is it ? . The 3.25 ratio is great and remember we drive at anywhere from 62mph to 70 mph (100 kph to 110 kph )  max here in Australia and not 80 mph like you guys do on your hwy s .

[barnett468]

235/60x15 tyres are the ones I would have on my Mach 1 not 215/70 x15 .  Depends one his rim width ,but should be at least a 7 inch .  Even a 235/60 can look small if the car sits high in the back .  That car should go ok now ,but we still don't know what intake it is ( dual plain or single ). And what Holley carb is it ? . The 3.25 ratio is great and remember we drive at anywhere from 62mph to 70 mph (100 kph to 110 kph )  max here in Australia and not 80 mph like you guys do on your hwy s .

i added to my post above . . i forgot to copy it from my word page . . yup, me too . . 235 or 245 . . the tallest and narrowest tires i have used just to get a near stock look was 215 x 65 - 15 . . i use a lot of 3.25 gears and 2000 stalls with all these tire sizes . . i always lower the cars at least 1" from stock too so they dont look dorky and dont have a lot of space between the tire and the wheel well.

perhaps if we can get him to run the 3.25 WITH the 235's he won't need to do any upgrades at all . . he will then have a 250 rpm increase at 60 mph and at least he could try it that way first, then decide . . also, as i mentioned earlier, if the tires are the correct width for the rims, it will corner a little better.

unfortunately, we can only go 80 mph in our dreams in california nowadays.

[BAC]

235/60x15 tyres are the ones I would have on my Mach 1 not 215/70 x15 .  Depends one his rim width ,but should be at least a 7 inch .  Even a 235/60 can look small if the car sits high in the back .  That car should go ok now ,but we still don't know what intake it is ( dual plain or single ). And what Holley carb is it ? . The 3.25 ratio is great and remember we drive at anywhere from 62mph to 70 mph (100 kph to 110 kph )  max here in Australia

yup, me too . . 235 or 245 . . the tallest and narrowest tires i have used just to get a near stock look was 215 x 65 - 15 . . i use a lot of 3.25 gears and 2000 stalls with all these tire sizes . . i always lower the cars at least 1" from stock too so they dont look dorky and dont have a lot of space between the tire and the wheel well.

perhaps if we can get him to run the 3.25 WITH the 235's he won't need to do any upgrades at all . . he will then have a 250 rpm increase at 60 mph and at least he could try it that way first, then decide . . also, as i mentioned earlier, if the tires are the correct width for the rims, it will corner a little better.

Gents, if I was starting from scratch I would be putting 235/60x15 tyres on the car, no question.  Unfortunately what I've got is almost brand new 215/70 tyres on 15x7" Magnum rims and I can't afford to start just throwing stuff away.  Just ditching the current tyres and keeping the rims isn't an option either as I wouldn't be comfortable squeezing 235 tyres onto 7" rims, especially since anything designed for an old car like the Mustang would probably have soft sidewalls.  The cost of a new set of 15x8" Magnums plus 235/60 Goodrichs would be somewhere north of $2.5K landed and I would be lucky to get $1K for mine if I could find a buyer.

I did make a breakthrough ID-ing the carby though.  Turns out it's a 570 CFM Street Avenger from the 4150 series with vacuum secondaries,  Holley part # 0-80570.  Is this under specced, or is it OK for the old 351W?  Would love to be able to tell you what intake it sits on, but unless anyone knows where to look for markings then I have no idea.  I can't even find any Ford Racing branded 4V intakes on the web to look at in order to make an educated guess.

If I was to change the diff gears to 3.25 plus get a new set of wheels and tyres I'd be looking at $3.5K all up, which is way more than I want to spend.  Even then, it's no sure thing it will make much difference to the seat of the pants dyno. So unless someone wants to give me $1.5K for my wheels and tyres, they will be staying on the car for the foreseeable future.

With the highway gearing, I can't see my old girl spending too much time on the freeways and even when she does it will be a max of 100 Km/h here in the Speed Camera State.  I did notice an ebay seller offering the Italian made Motive diff gears for $325 delivered - is that a good price?  Guess it would still be at least a grand all up once you factor in labour and fluid...

[GLENN 70]

Ok where getting some where    a 570 is a good carby but might be a bit small for your 351 but seeing you just want more hit off the line it should be ok . It's most likely a dual plain intake .  If your happy with 2700 rpm at 100 kph and its ok as you really dont do hwy driving a 3.5 ratio . Your tyres will out last you by the sounds of it . 15x7 is std for magnum 500 rims but a 235/60 will still fit ok . See what the others say about the 3.5 ratio . If you had lower profile tyres I would say a 3.25 ratio .  I think a 670 would be better .